Conventional polymer electrolyte fuel cells concurrently generate electric power and heat by an electrochemical reaction between a fuel gas containing hydrogen and an oxidant gas containing oxygen, such as air, and there are various types thereof according to the fuel for use therein, the constituent material thereof, and the like.
FIG. 9 is a fragmentary section of a conventional polymer electrolyte fuel cell. The polymer electrolyte fuel cell 100 is a structure having a plurality of stacked cells 102 and has a refrigerant manifold 104 (refrigerant channel) through which a refrigerant recovering the generated heat flows.
The cells 102 each have a polymer electrolyte membrane 106 composed of cation-exchange resin that selectively transports a hydrogen ion and conductive separators 108 placed on both sides of the polymer electrolyte membrane 106. Each cell 102 has an anode joined onto one surface of the polymer electrolyte membrane 106 that faces one of the separators 108 and a cathode joined onto the other surface of the polymer electrolyte membrane 106 that faces the other of the separators 108, though both are not shown. A composition of the polymer electrolyte membrane 106, the anode, and the cathode is referred to as MEA (Membrane Electrode Assembly).
The refrigerant manifold 104 is formed by connecting among penetration holes formed through the polymer electrolyte membranes 106 and the separators 108 of the cells 102. The refrigerant that has flowed through the refrigerant manifold 104 flows into refrigerant channels 110 provided in the cells 102 and recovers heat from the cells 102.
With use of an ionic conductor such as tap water as the refrigerant, a short circuit may occur through the refrigerant between cells 102 spaced apart from each other with one or more cells 102 interposed therebetween (e.g., first cell and third cell from upstream side with respect to a flow direction of the refrigerant that is shown by outline arrows in FIG. 9), and the separators 108 of the cell 102 on high voltage side may thereby deteriorate because of a current corrosion thereon. This is caused by occurrence of an oxidation reaction on interfaces between the cell 102 on the high voltage side and the ionic conductor. On condition that progress of the current corrosion on the separators 108 causes a deterioration of parts of the separators 108 that are in contact with seal members 112 for sealing the refrigerant, there is a possibility that a degradation in the sealability for the refrigerant between the seal members 112 and the separators 108 may cause leakage of the refrigerant to the outside. Similarly, there is a possibility that the short circuit through the refrigerant may cause a degradation in sealability attained by seal members 114, 116 for the fuel gas, the oxidant gas and the like.
As a measure against this problem in a polymer electrolyte fuel cell disclosed in Patent Literature 1, a refrigerant channel is provided so that the length of the channel for refrigerant is prolonged in order to provide the refrigerant with high resistivity.
In a polymer electrolyte fuel cell disclosed in Patent Literature 2, a sacrifice material that is more prone to undergo the current corrosion than separators is provided in a refrigerant channel in a current collector on the high voltage side.
In a polymer electrolyte fuel cell disclosed in Patent Literature 3, a member that is to be at higher potential than the highest-potential cell is provided in a refrigerant channel.
For another measure, pure water can be used as refrigerant.